I got interested in sheating when I discovered Angra D, a probable late 16th century galleon whose below-the waterline hull, keel and sternpost were all covered in lead.
This was further compounded when I discovered and excavated the remains of the HMS Pallas, beached and burned in the Azores in 1782, after escaping shipwreck at high seas, like the rest of her party:
https://historycollection.com/20-naval-disasters-from-history-that-make-us-scared-to-sail/3/
And why sheating? Because I read the court martial of the Pallas captain and in it they said that the frigate's carpenter had found out that all her iron fasteners had "shrunk" and had "got thin as a toothpick".
What had happened? The British had coppered all those ships. But they had maintained their iron fasteners.
Now, when you immerse copper with iron in a salt bath, aka seawater, you have a battery. And galvanic corrosion (that's why we have to have a zinc piece on our outboard engine so that it can die for all other more valuable metals on the engine).
All that copper stood shining, while all the iron was slowly being dissolved into iron oxides and ions. And the ship´s timbers gave way, spat the caulking and water entered. A lot of water.
How do you solve that problem?
By using the same metals, both in sheating and in fastening - it finally was found that if you wanted long lasting copper sheathing to protect your hull, you had to go with copper fastening.
Yes, bronze is much more expensive than iron, but the benefits - ships that last the double, are more watertight and are faster because copper is toxic to the marine life that usually grows on hulls) really outweighted the extra costs.
Pure copper was used up through the 1830s when "Muntz Metal" was patented. Muntz metal was a copper alloy of copper and zinc, cheaper then pure copper (other names for Muntz
metal are "admiralty brass" and "yellow metal")
Yes, the use of copper for ship fasteners dates back to the classical era, and they appear on wrecks dating to the 5th and 4th centuries B.C. in the form of clenched nails, of pure copper. The Tektas Burnu, Ma'agan Mikhael, and Kyrenia ships are examples of this, with their fastenings are made of pure copper (with its natural impurities or trace elements, such as zinc, lead, nickel, andarsenic).
By the Roman era, iron replaced copper in shipbuilding , due to its greater strength and lesser cost. Fasteners of iron or wood remained the standard through the medieval and early modern eras until the last quarter of the 18th century.
I once wrote this on the subject:
"The effect of copper was to keep the ships relatively free of seaweed, and thus improve their sailing performance, while at the same time it afforded better protection for the timbers against the ravages of than the existing sheathing.
Probably the most important technical innovation to be implemented by the naval protagonists during the American War of Independence was the sheathing of ship's hulls with copper, and it was the British who developed this technique and held the initiative.
Back in 1708, Charles Perry proposed the idea of copper sheathing, but the concept was rejected because of the costs involved. Again, in 1740, Nehemiah Champion suggested using sheets of "brass lateen" as sheathing, and although such an experiment was apparently made, nothing came out of it. Eighteen years later, the Royal Navy conducted an experimental coppering on the false keel of the HMS Invincible and then proceeded, in 1759, to use copper plates in the sternpost and keels of some of it's warships.
The first ship ever fully sheathed in copper was the 32-gun English frigate, HMS Alarm, in 1761. Following a careful assessment made in 1763 of its effectiveness - after the ships had done service in the
West Indies for two years - the Admiralty decided to repeat the process on two other ships, the Dolphin and the Tamar. This was done in 1764, but in 1766 the Alarm was surveyed again, and many flaws and problems were discovered, the major problem being the damage done by the coppering to the iron bolts due to the galvanic activity generated between the iron and the copper. Following the detection of similar problems on the Dolphin and Tamar, copper sheathing was removed on all three ships.
By 1775, the Navy Board began to show renewed interest in the copper sheathing, a fact that might have been compounded by the inability of the timber contractors to supply enough sheathing board. In the next two years a number of small ships were sent off in voyages with copper bottoms with "composition" to protect the iron bolts from corrosion and, by the end of 1776 one 32-gun frigate, four 20´s and a sloop had been coppered. On all of these ships, the bottom was painted with a mixture of white lead and linseed oil, on which the copper plates were to be fixed with nails made of an alloy which included copper. The same material was used to make the braces and pintles while the false keel was fixed to the main keel with copper staples with a thin sheet of lead between them.
A few more English ships were coppered in 1778, and by 1778 the trend had caught on and more and more ships were being coppered, with those already sheathed impressing the sea officers by their handling capabilities.
Finally, in 1779, orders were issued in that all ships of 32 guns and less should be coppered the next time they were in dock, although no solution to the corrosion of iron bolts had yet appeared and copper bolts were trusted only for ships of fifth and sixth rates. The reason for this move was that an apparently successful protection for iron bolts had been found, by the creation of a watertight barrier between the copper and the iron bolts. This barrier consisted in the application of thick paper - soaked in oil of tar and in Dawson´s composition - between the copper plates and the hull, an experiment
first carried out on a 44-gun ship, the HMS Jupiter. By then, the ships that were copper sheathed were described as "felted and yellow metaled" because the copper protected the felt and tar layer.
Later, it was decided that the whole battle fleet should be coppered. In January 1782, eighty-two capital ships, fourteen of 50 guns, hundred and fifteen frigates and one hundred and two sloops and
cutters had been coppered to that time. However, at the end of that year, doubts about the effectiveness of the protection of iron bolts from the corrosive effects of the copper were raised very forcibly.
The chief reason was the violent storm of September 1782 off the Banks of Newfoundland, when the captured French ships, the Ville de Paris (110) and the Glorieux (74), and the British Ramillies (74) and Centaur (74) all foundered with the loss of 3500 lives. A thorough inspection of the 74-gun ships Edgar, Fortitude and Alexander showed irrefutably that the iron bolts of all three ships were in a dangerous condition.
Another major weakness was the lack of protection which the copper provided against the worm, most notably in the stern area, because neither copper nails nor copper cladding did much to keep teredo worms out of the hull timber. It was the tar soaked felt, applied hot to the hull, that formed a layer impenetrable to the teredo in its planktonic phase. In some hulls that have had copper applied without the felt, the copper seemed to provide a protective layer behind which the worms did their worst, coming to the surface of the wood with impunity.
It was only in December 1783 that the new copper and zinc bolt, hardened by mechanical means and developed by William Forbes, entered in service. By August 1786, all ships were changed to the new bolts.
From the 1780's to the 1830's copper-fastened and sheathed vessels became more common, particularly for naval vessels and larger merchant craft, but the great expense and short life span of pure copper plates were still a problem and kept this type of sheathing from being widely adapted. The problems were finally overcome in 1832, when George F. Muntz of England patented 'yellow metal' or 'Muntz metal', an alloy of 60% copper and 40% zinc, that was hot-rolled into thin sheathing plates. Muntz's alloy was flexible enough to adapt itself to a wooden hull, corroded at a much slower rate than copper, and because of the high percentage of inexpensive zinc cost substantially less than pure copper. Muntz aggressively marketed his new alloy during the 1830's, and it began to see widespread use by the 1840's.
For a general analysis on sheating, go here, starting p. 76:
https://nautarch.tamu.edu/Theses/pdf-files/Jones-MA2004.pdf
For a discussion on lead sheathing, here:
http://etd.fcla.edu/WF/WFE0000360/Marr_Andrew_Wallace_201301_MA.pdf
For a discussion on the fate of the Pallas, go here, after p. 77:
http://oaktrust.library.tamu.edu/bi...u-2006A-ANTH-Flynn.pdf?sequence=1&isAllowed=y
Here, some excerpts from M. MacCharty's book on ship fasteners:
"One of the first attempts to apply these new alloys to shipbuilding appeared in 1779, apparently as a result of experiments on what was then called "Chinese copper."
The industrial chemist James Keir of Birmingham, in association with Matthew Boulton, conducted these trials. . . . In 1782, Keir decided to work through William Forbes, the existing copper contractorfor the navy in pursuing his design, and further trials of his bolts and some rudder braces of the same composition were held at Deptford in November, 1783. The following month Forbes informed Keir that the Navy had rejected his bolts for they had proved excessively brittle. They also informed him that they were finding "bolts of pure copper" and a form of "copper and zinc bolt hardened by mechanical means" to be superior.
Many solutions were offered including the substitution of iron fastenings with copper below the waterline, but copper was not able to be driven through the timbers without experiencing bending, breaking, or at best severe distortion at the head. A harder metal was sought either by developing new alloys or by forging the copper in some new way that would increase its toughness. For a while "mixed metal" was tried. Writing his analysis titled A History of Naval Architecture, Fincham advised that in August, 1783, all ships from 44s down were ordered to be fastened with "mixed metal." This was a short-lived solution, as will be seen.
Mixed metal fastenings apparently had good holding power and were resistant to oxidation, but for a period what soon became acknowledged as the "brittleness of mixed metal" prevented them being generally used except where there was little choice. An example is the American frigate Essex. It was built in a period of British embargo on strategic materials like copper, and it is interesting to note that Paul Revere, who supplied the fastenings for Essex, refers to the "composition metal" then being used as a substitute being a brittle mix of copper and tin. Later, among some American builders, the term "composition metal" was used to describe copper alloy fastenings generally. Thus while the constituents of "mixed metal" and "composition metal" appear to have varied over place and time, it is
nonetheless evident that "mixed metal" in its mid-nineteenth-century form was unsuitable for large fastenings due to its brittle nature.
As a result, brass, a very hard binary alloy of copper and zinc, came to be considered a possibility for a while. Two methods of production were used at the time. In the "direct method," the two metals were melted in crucibles or furnaces and after mixing were poured into sand molds as "thin slab ingots" that were heated in an open coal fire and then reduced by hammering by a "battery" of tilt hammers. The ancient and difficult form of "calamine brass," was prepared without melting the copper. The product was in demand until around 1750 for objects that were enhanced by its
"characteristic" golden appearance, such as "gilt" buttons.
Workers preferred the "red brasses" of between 10 to 20 percent zinc to the yellow brasses consisting of a larger proportion of zinc, because the addition of more zinc (though it represented an enormous saving over the far more expensive copper) caused the metal to be progressively harder and difficult to produce.
Brass will roll hot in mixtures ranging from fifty to sixty-three parts copper to thirty-seven to fifty zinc, and in trials he came to favor an alloy later called "Keir's Metal".
Keir's "compound metal" bolts were tested on two RN vessels being built at the time but were found to be "insufficiently malleable." In 1782, Keir decided to work through William Forbes, the existing copper contractor for the navy in pursuing his design, and further trials of his bolts and some rudder braces of the same composition were held at Deptford in November, 1783. The following month Forbes informed Keir that the Navy had rejected his bolts for they had proved excessively brittle. They also informed him that they were finding "bolts of pure copper" and a form of "copper and zinc
bolt hardened by mechanical means" to be superior.
1783 is a signal date in the evolution of ship's fastenings, for Forbes, who was apparently "experimenting independently" of Keir, attempted to solve the problems himself by applying the patent of another naval contractor, Henry Cort. It will be recalled that this was lodged in that year for improving iron and compressing out the impurities by drawing it through grooved rollers. In succeeding with the application of the method to copper, Forbes took out a patent for ships' bolts and fastenings of copper in July, 1783. According to Harris, "He used a spelter and copper alloy, or for cases where hardness was not so important, pure copper. The metal, made into bars, was to be passed through grooves of successively smaller size; the mixed metal would be rolled cold, the copper either hot or cold. In
order to produce bolts by this method he would need to drive rolls, and work a tilting hammer to give the final shape."
As indicated, Fincham advised that in August, 1783, all ships from 44s down were ordered to be fastened with mixed metal, but an Admiralty order of the next month stated that new ships were to be constructed using metal bolts (metal in this case being hardened pure copper), while existing ships were to have the iron replaced. In October of the same year copper bolts were ordered for all classes of ships.
Thus the use of what came to be termed "metal bolts" was sanctioned by the Royal Navy, and they came to be required on all frigates of 44 guns and under. ... .. It was a period of great experimentation, and while "elasticity tests" were "still being carried out" on the fastenings supplied in this period, they soon came to exceed expectations. The final order to change over to the new bolts came in August, 1786, when the Admiralty ordered all guard ships to be copper fastened, with alloy to be used only for braces and sheathing tacks. Thus the period of experimentation ceased and copper fastenings
became the norm where naval ships were to be sheathed with copper. . . .
Following what were described as "sporadic and unsuccessful" efforts by scientists like Humphrey Davy and by "metal smelters and rollers" such as those individuals and companies mentioned previously, to prolong the life of copper sheathing and find a substitute for it, manufacturers began experimenting with copper alloys. In 1800, for example, William Collins had patented processes for making copper alloy sheets to be rolled at "red-heat" of various composition that came to be called "red, yellow, and white" sheathing. The white hue may have been due to the coloring effect when the
alloy contains less than 40 percent copper. Equally, it may have been a result of the presence of nickel in the alloy. The other types were a copper-zinc alloy fifty parts copper to forty parts zinc mixed with what were described as ten parts of unspecified "other metals." This new element in experimentation with sheathing constituents and manufacture and the earlier work of James Keir, led eventually to the brilliant career of the Birmingham-based George Frederick Muntz . . . settling on one that proved spectacularly successful in a ratio of copper to zinc that was close to 60:40. Apparently the 60:40 process was found by accident when a "careless workman mixed metals contrary to order." Marveling at the relative ease that the 60:40 mix could be rolled into sheets while red-hot, in October, 1832, Muntz secured patents to the rights to manufacture and sell this "yellow metal," as it also came to be called, as a sheathing and fastening for ships.
Although its advantages were obvious, there was inevitably some opposition from what Muntz himself termed "the cloven foot of the copper trade," and as a result Flick records that it took Muntz over one-third of the life of the fourteen-year patent afforded to him to establish the worth of his product. Eventually, as the business outgrew Muntz's own rolling mill in Birmingham, he joined in partnership with Pascoe Grenfell and Sons ,who produced it at their Swansea mill as Muntz's Patent Metal Company. They and other partners then fixed the prices of the alloy at Ł18 per ton lower than
the market price for the equivalent copper product, serving to establish Muntz metal as the sheathing of choice where transport costs still kept it as an efficient competitor. As an example of their success in entering the market, fifty ships were metaled with Muntz metal in 1837, over 100 in 1838, doubling in 1840, and doubling yet again by 1844.
With Muntz successfully supervising the manufacturing operations, by 1840 the company employed thirty men to smelt and roll the alloy and was producing 2,000 tons yearly. Three years later the company had over 200 men producing 3,000 to 4,000 tons yearly at Ł8 per ton profit. In 1842, the partnership with Pascoe Greenfell and Sons had been terminated with some acrimony, and when Muntz's patent expired in 1846 they and others began making sheathing in the same 60:40 mix. While names like "yellow metal" then came into vogue, the term "Muntz metal" is regularly used
wherever an alloy is found to comply with his patent."
